This is a cancer affecting the mammary glands that is most commonly seen in older entire female cats (although it can also be seen in male cats and neutered female cats).
The tumour commonly affects more than one of the mammary glands, which often develop multiple firm swellings or nodules, and the skin over these nodules and masses often becomes ulcerated over time.
This tumour commonly spreads to the local lymph nodes and can also spread to the lungs.
Early treatment of small tumours is likely to be much more successful than if multiple or larger tumours are present (where local and distant spread of the tumour is much more likely to have occurred).
Treatment is usually by surgical removal of the tumour and associated tissues, and there may also be a role for chemotherapy in some cases.